Day: August 4, 2016

Slit lamps are prohibitively expensive in the third world areas of India where they are most needed. An invention that’s been around for over a hundred years, the slit lamp is a simple-in-concept way to see and diagnose a large array of ocular issues.

Since they are relatively old by technological standards, the principles behind them have become more and more understood as time has gone on. While a nice lab version with a corneal microscope is certainly better, innovations in manufacturing have brought the theoretical minimum cost of the device way down, or at least that’s what [Kewal Chand Swami] hopes.

His design aims for portability and cost reduction. It must be able to travel to remote locations and it must be significantly cheaper than the lab versions. It uses off-the-shelf lenses in a 3D printed housing with a simple LED torch, the kind you can buy for a dollar at the check-out stand.

The assembly slides onto the user’s head and is held there with straps. The doctor can adjust where the slit the lamp shines and also look through a microscope to diagnose the issue. Hopefully devices like this will see similar community support to the prosthetic projects we’ve covered.

It’s frustrating, the reluctance of some of my fellow hackspace members to put the cordless drill battery back in the charger after use. As this is being written I’ve just coaxed enough energy from the drill to make a few holes in a piece of PVC pipe that will form part of an improvised flagpole, and upon that pole will hang Hackaday’s Jolly Wrencher flag at this weekend’s EMF Camp. We’re sharing a village with Oxford Hackspace, and as both your Hackaday scribe and an OxHack member the last week has been a little busy.

In theory it’s a simple enough process, getting a hackspace and all its assorted accoutrements down to Guildford. Three or four members’ cars will be loaded to the gunwales and will set off in good time to have everything under way without still desperately getting ready when the fun begins. In practice it’s been a procession of narrowly averted disasters, from the gazebo someone bought at auction turning out to have five walls and no roof, to the large ball that forms an essential part of one of the projects OxHack will be featuring being a buy-while-stocks-last remaindered product from last years Argos catalogue that only certain stores seem to still have.

We’ll be on the border between camping areas A and B, next to our friends from the Netherlands. I’m told that this location was requested due to likely proximity to a source of stroopwafels. If you come along on Friday between 6 and 8 PM we’re holding the Tindie bring-a-hack event, at which we’ll be inviting attendees to bring along their hacks to share with the masses. All projects are welcome, but if you have a Hackaday Prize entry, a Hackaday.io project or a Tindie item we’d especially love to see you. My colleague Jasmine assures me that there will be a limited amount of Hackaday and Tindie swag on offer.

If you’re going down to EMF Camp this weekend then please drop by and have a chat if you’re passing our village. Otherwise you’ll probably encounter us on our travels as we try to seek out the interesting projects and hacks to feature on these pages. We hope the British weather doesn’t deliver any unpleasant surprises, and may all your projects work when you demonstrate them in front of the masses!

Jenny List is a director of Oxford Hackspace when she is not writing for Hackaday.

We toss together our own PCB designs, throwing in a microcontroller here or there. Anything more demanding than that, and we reach for a Raspberry Pi or BeagleBone (or an old Linksys router). Why don’t we just whip together a PCB for a small Linux computer? Because we don’t know how…but [Jonas] apparently does. And when we asked him why he did it, he replied “because I can!”

His Ethernet-to-6LoWPAN gateway project is a small, OpenWRT-capable Linux computer in disguise. Rather than yet another Raspberry Pi project, he designed around an Atmel AT91SAM9G25 400 MHz CPU, and added some memory, Ethernet, and a CC2520 radio chip to handle the wireless side. It’s all done on a four-layer board, and hotplate/skillet reflowed. This seems temptingly like something within our reach. [Jonas] had access to X-ray machines to double-check his reflow work, which probably isn’t necessary, although it looks really cool.

When finished, the project will link together a 6LoWPAN network (probably home automation) and his home wired network. That makes this device a rival to something like Philips’ Hue Bridge, which was the subject of some controversy when they locked out other devices for a few days until they recanted. Indeed, in response to this, there’s been quite a lot of effort at hacking the firmware of the Hue device, just to stay on the safe side in case Philips plays shenanigans again.

Soon, that’s not going to be necessary. [Jonas]’s design is open from the ground up, and coupled with open software running on top of the OpenWRT router operating system, that’s the full stack. And that’s great news for folks who are thinking about investing in a home automation technology, but afraid of what happens then the faceless corporations decide to pull the plug on their devices.

The Raspberry Pi is a great computer, even if it doesn’t have SATA. For those of us who have lost a few SD cards to the inevitable corruption that comes from not shutting a Pi down properly, here’s something for you: USB Mass Storage Booting for the Raspberry Pi 3.

For the Raspberry Pi 1, 2, Compute Module, and Zero, there are two boot modes – SD boot, and USB Device boot, with USB Device boot only found on the Compute Module. [Gordon] over at the Raspberry Pi foundation spent a lot of time working on the Broadcom 2837 used in the Raspberry Pi 3, and found enough space in 32 kB to include SD boot, eMMC boot, SPI boot, NAND flash, FAT filesystem, GUID and MBR partitions, USB device, USB host, Ethernet device, and mass storage device support. You can now boot the Raspberry Pi 3 from just about anything.

The documentation for these new boot modes goes over the process of how to put an image on a USB thumb drive. It’s not too terribly different from the process of putting an image on an SD card, and the process will be streamlined somewhat in the next release of rpi-update. Some USB thumb drives do not work, but as long as you stick with a Sandisk or Samsung, you should be okay.

More interesting than USB booting is the ability for the Pi 3 to boot over the network. Booting over a network is nothing new – the Apple II could do it uphill both ways in the snow, but the most common use for the Pi is a dumb media player that connects to all your movies on network storage. With network booting, you can easily throw a Pi on a second TV and play all that media in a second room. Check out the network booting tutorial here.

Everyone wants their prototypes to look polished, as opposed to looking like 3D-squirted weekend afterthoughts. The combination of Delrin and a Laser Cutter make this easy, especially if you learn a few tricks-of-the-trade that will make your assemply pop, both functionally and aesthetically.

If you’re just getting started in this domain, let me introduce you to two classic techniques for laser-cut prototypes: puzzle-piecing and the T-nut-slotting. While these techniques are tried-and-true, I hope, fearless reader, that they’ll leave you hungry for something cleaner, something more refined. If that’s the case, read on!

Sometimes there’s just no substitute for the right diagnostic tool. [Ankit] was trying to port some I2C code from an Arduino platform to an ARM chip. When the latter code wasn’t working, he got clever and wrote a small sketch for the Arduino which would echo each byte that came across I2C out to the serial line. The bytes all looked right, yet the OLED still wasn’t working.

Time to bring out the right tool for the job: a logic analyzer or oscilloscope. Once he did that, the problem was obvious (see banner image — Arduino on top, ARM on bottom): he misunderstood what the ARM code was doing and was accidentally sending an I2C stop/start signal between two bytes. With that figured, he was on the right track in no time.

We just ran an epic post on troubleshooting I2C, and we’ll absolutely attest to the utility of having a scope or logic analyzer on hand when debugging communications. If you suspect that the bits aren’t going where they’re supposed to, there’s one way to find out. It’s conceivable that [Ankit] could have dug his way through the AVR’s hardware I2C peripheral documentation and managed to find the status codes that would have also given him the same insight, but it’s often the case that putting a scope on it is the quick and easy way out.

The first time I was in school for electrical engineering (long story), I had a professor who had never worked in the industry. I was in her class and the topic of the day was measuring AC waveforms. We got to see some sine waves centered on zero volts and were taught that the peak voltage was the magnitude of the voltage above zero. The peak to peak was the voltage from–surprise–the top peak to the bottom peak, which was double the peak voltage. Then there was root-mean-square (RMS) voltage. For those nice sine waves, you took the peak voltage and divided by the square root of two, 1.414 or so.

You know that kid in the front of the class? They were in your class, too. Always raising their hand with some question. That kid raised his hand and asked the simple question: why do we care about RMS voltage? I was stunned when I heard the professor answer, “I think it is because it is so easy to divide by the square root of two.”